A method for producing a molded material by using a reinforcing material, such as thermosetting epoxy resin, unsaturated polyester resin, polyamide resin, or phenol resin, for fiber materials such as carbon fiber and glass fiber is well known. The fiber-reinforced plastic obtained by using this method is extensively used for a material of structures such as an airplane and a ship, and sporting goods such as a tennis racket and a golf club. The epoxy resin used as a reinforcing material, which is not only excellent in adhesive properties, heat resistance and chemical resistance, but also is inexpensive, is often used as a well balanced material.
The epoxy resin composition has an excellent electric performance and adhesive properties. However, in cases where sufficient heat resistance can not be obtained by using a conventional epoxy resin, a cyanate-epoxy composite resin composition having high heat resistance, which is obtained by further blending with a cyanate resin, is often used for a sealing material of a semiconductor, or for molding of electronic circuit substrate etc.
With regard to a method for curing by using epoxy resin and cyanate resin, it is known that a cured product for sealing a semiconductor which has a high glass-transition temperature, low water absorption coefficient and good adhesive properties can be obtained by using phenol-modified resin as a curing agent (for example, Patent document 1 etc.). However, in cases of using this method, although adhesive properties and heat resistance of a cured product are good, there is a disadvantage in that, since the stretch displacement of the cured product is low, the cured product cannot adapt to the fiber's stretch when it is applied to a fiber material, and as a result, an internal peel-off is caused.
In addition, a method for producing a cyanate-epoxy composite resin composition is known that has excellent storage stability and curing properties and also is suitable for a sealing agent or an adhesive agent for a semiconductor, by carrying out the curing reaction, using a latent curing agent which is obtained by reacting an epoxy compound with a polyamine compound (for example, Patent document 2 etc.). However, in this method a powdery latent curing agent is used, therefore, there is a disadvantage in that, when the resin composition is applied to a fiber material, the curing agent cannot permeate into the inside of the fiber, and as a result, the curing is not carried out enough.
Furthermore, with regard to a method which can rapidly carry out a curing reaction of an epoxy resin with a cyanate resin, a method using an adhesive agent which can bond resin materials in a short time is known, wherein a laser beam is irradiated to a composition which contains a latent curing agent obtained by reacting polyamine with epoxy resin, together with a light-absorbing component (for example, Patent document 3 etc.). This method is a method which can realize a bonding in a shorter time compared to conventional thermal curing by using resin materials having light transmission properties and transmitting a laser beam to the inside of the adhesion part. However, in the case of being applied as a composition for fiber-reinforced plastic, there is a disadvantage in that, since a latent curing agent used as a curing agent, and a light-absorbing component are solid powder, a latent curing agent and a light-absorbing component remain on the surface without permeating into the inside gap existing among fibers, therefore, curing of resin in the inside gap among fibers becomes insufficient.